PROJECT SUMMARY/ABSTRACT Transcriptional and Translational Regulation in Erythropoiesis Project 2 - Patrick G. Gallagher, PI Erythrocytes are highly specialized cells that have evolved to efficiently carry out their primary functions of oxygen transport and delivery. Unique patterns of gene regulation and expression direct a precise ensemble of proteins required for erythrocyte structure and function. The overall goal of this proposal is to characterize and integrate data from transcription, epigenetic, and translation-based studies in human erythroid cells of differing developmental and differentiation stage to advance of our understanding of normal and perturbed erythropoiesis. In specific aim one, chromatin architecture, DNA methylation status, and genomic organization will be correlated with programs of gene expression at different stages of erythropoiesis. These studies will address the hypothesis that varying epigenetic patterns determine programs of gene expression influencing erythroid cell development and differentiation. Stage-specific enhancer repertoires will be identified and enhancers correlated with genes associated with known erythroid cell traits and diseases. Correlative studies will be performed in a TET2-deficient model of myelodysplastic syndrome (MDS), in uncultured primary erythroid cells isolated from bone marrow of TET2-mutant MDS patients, and erythroid cells with altered lamin A and lamin B1 levels across terminal erythroid differentiation. Control of gene expression at the level of translation is now recognized to be as important as transcriptional regulation. In specific aim two, profiles of proteins undergoing mRNA translation and their abundance will be characterized during erythropoiesis. Defining and characterizing the abundance of proteins translated at differing stages of erythropoiesis will provide novel insights into protein structure, function, and abundance throughout erythroid commitment, development, and differentiation. These studies will address the hypothesis that varying patterns of mRNA translation, determined by stage-specific regulatory programs, determine the programs of protein expression that play critical roles in homeostatic cell growth and proliferation and specific patterns of dysregulated translation are associated with inherited hematologic disease. Protein profiles obtained by ribosomal profiling will be correlated with mRNA expression, epigenetic, and proteomics data sets. Correlative studies will be performed to assess the influence of RPL5 or RPL11 deficiency on ribosomal profiles on a global, cellular stage-specific scale in a model of Diamond Blackfan anemia. Integration of data from combinations of transcription, epigenetic, translational and metabolic-based studies will allow hematology investigators to create and compare high-resolution, global maps of relevant interactions driving gene expression and protein production in erythroid cells of differing differentiation and developmental stage, and normal and abnormal state.